冲压变形模具外文文献翻译中英文翻译外文翻译Word格式.docx
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冲压变形模具外文文献翻译中英文翻译外文翻译Word格式.docx
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Cuttingisashearingprocessthatonepartoftheblankiscutformtheother.Itmainlyincludesblanking,punching,trimming,partingandshaving,wherepunchingandblankingarethemostwidelyused.Formingisaprocessthatonepartoftheblankhassomedisplacementformtheother.Itmainlyincludesdeepdrawing,bending,localforming,bulging,flanging,necking,sizingandspinning.
Insubstance,stampingformingissuchthattheplasticdeformationoccursinthedeformationzoneofthestampingblankcausedbytheexternalforce.Thestressstateanddeformationcharacteristicofthedeformationzonearethebasicfactorstodecidethepropertiesofthestampingforming.Basedonthestressstateanddeformationcharacteristicsofthedeformationzone,theformingmethodscanbedividedintoseveralcategorieswiththesameformingpropertiesandtobestudiedsystematically.
Thedeformationzoneinalmostalltypesofstampingformingisintheplanestressstate.Usuallythereisnoforceoronlysmallforceappliedontheblanksurface.Whenitisassumedthatthestressperpendiculartotheblanksurfaceequaltozero,twoprincipalstressesperpendiculartoeachotherandactontheblanksurfaceproducetheplasticdeformationofthematerial.Duetothesmallthicknessoftheblank,itisassumedapproximatelythatthetwoprincipalstressesdistributeuniformlyalongthethicknessdirection.Basedonthisanalysis,thestressstateandthedeformationcharacteristicsofthedeformationzoneinallkindofstampingformingcanbedenotedbythepointinthecoordinatesoftheplaneprincipalstress(diagramofthestampingstress)andthecoordinatesofthecorrespondingplaneprincipalstains(diagramofthestampingstrain).Thedifferentpointsinthefiguresofthestampingstressandstrainpossessdifferentstressstateanddeformationcharacteristics.
Whenthedeformationzoneofthestampingblankissubjectedtoplanetensilestresses,itcanbedividedintotwocases,thatisσγ>
σθ>
0,σt=0andσθ>
σγ>
0,σt=0.Inbothcases,thestresswiththemaximumabsolutevalueisalwaysatensilestress.Thesetwocasesareanalyzedrespectivelyasfollows.
2)Inthecasethatσγ>
0andσt=0,accordingtotheintegraltheory,therelationshipsbetweenstressesandstrainsare:
εγ/(σγ-σm)=εθ/(σθ-σm)=εt/(σt-σm)=k(1.1)
where,εγ,εθ,εtaretheprincipalstrainsoftheradial,tangentialandthicknessdirectionsoftheaxialsymmetricalstampingforming;
σγ,σθandσtaretheprincipalstressesoftheradial,tangentialandthicknessdirectionsoftheaxialsymmetricalstampingforming;
σmistheaveragestress,σm=(σγ+σθ+σt)/3;
kisaconstant.
Inplanestressstate,Equation1.1
3εγ/(2σγ-σθ)=3εθ/(2σθ-σt)=3εt/[-(σt+σθ)]=k(1.2)
Sinceσγ>
0,so2σγ-σθ>
0andεθ>
0.Itindicatesthatinplanestressstatewithtwoaxialtensilestresses,ifthetensilestresswiththemaximumabsolutevalueisσγ,theprincipalstraininthisdirectionmustbepositive,thatis,thedeformationbelongstotensileforming.
Inaddition,becauseσγ>
0,therefore-(σt+σθ)<
0andεt<
0.Thestraininthethicknessdirectionoftheblankεtisnegative,thatis,thedeformationbelongstocompressiveforming,andthethicknessdecreases.
Thedeformationconditioninthetangentialdirectiondependsonthevaluesofσγandσθ.Whenσγ=2σθ,εθ=0;
whenσγ>
2σθ,εθ<
0;
andwhenσγ<
2σθ,εθ>
0.
Therangeofσθisσγ>
=σθ>
=0.Intheequibiaxialtensilestressstateσγ=σθ,accordingtoEquation1.2,εγ=εθ>
0andεt
<
0.Intheuniaxialtensilestressstateσθ=0,accordingtoEquation1.2εθ=-εγ/2.
Accordingtoaboveanalysis,itisknownthatthiskindofdeformationconditionisintheregionAONofthediagramofthediagramofthestampingstrain(seeFig.1.1),andintheregionGOHofthediagramofthestampingstress(seeFig.1.2).
2)Whenσθ>
0andσt=0,accordingtoEquation1.2,2σθ>
0,Thisresultshowsthatfortheplanestressstatewithtwotensilestresses,whentheabsolustevalueofσθisthestraininthisdirectionmustbepositive,thatis,itmustbeinthestateoftensileforming.
Alsobecauseσγ>
0.Thestraininthethicknessdirectionoftheblankεtisnegative,orinthestateofcompressiveforming,andthethicknessdecreases.
Thedeformationconditionintheradialdirectiondependsonthevaluesofσγandσθ.Whenσθ=2σγ,εγ0;
whenσθ>
σγ,εγ<
0;
andwhenσθ<
2σγ,εγ>
Therangeofσγisσθ>
=σγ>
=0.Whenσγ=σθ,εγ=εθ>
0,thatis,inequibiaxialtensilestressstate,thetensiledeformationwiththesamevaluesoccursinthetwotensilestressdirections;
whenσγ=0,εγ=-εθ/2,thatis,inuniaxialtensilestressstate,thedeformationcharacteristicinthiscaseisthesame
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